Microsoft has acquired Winternals Software, the company co-founded by rootkit detective Mark Russinovich.

Russinovich and Bryce Cogswell founded the 85-person software company in 1996. Winternals produces a number of enterprise-system, recover- and performance-tuning software products.

The company also hosts a popular freeware site called Sysinternals.com that boasts 10,000 registered users and about 1 million page views per month.

Terms of the acquisition, which was announced Tuesday, were not disclosed.

Russinovich made international headlines last November after he discovered that copy protection software that Sony Corp. had been distributing with millions of CDs was cloaking itself using undetectable "rootkit" software.

Sony was ultimately forced to recall the affected CDs after hackers began using the rootkit to hide malicious code.

Microsoft would not say much about what it plans to do with the Winternals product family or with the Sysinternals freeware, but the software giant plans to eventually move the company's Austin, Texas, operations to Redmond, Washington.

Winternals customers will continue to be supported through the end of their contracts, but expired contracts cannot be renewed, Microsoft said.

For the time being, however, Russinovich will maintain his widely read blog on the Systernals Web site. "I will definitely keep blogging," he said. "Sysinternals.com is where the blog will be up until when and if Microsoft decides to move the site."

Russinovich will become one of 14 technical fellows within Microsoft, working in the Microsoft's Platforms & Services Division. Cogswell will assume the role of software architect within the Windows Component Platform Team.

In his new role, Russinovich will help chart the future direction of the Windows platform as it adopts new virtualisation, security and multicore processor capabilities.

"For the last 10 years we've been working on Windows and Windows platform technologies," Russinovich said. "Now we'll have the opportunity to directly influence Windows and Windows platform products."

He thinks Microsoft will continue to develop the software that his company created. "We felt that Microsoft was the ideal vehicle to getting those technologies to a broader audience," he said.